Endodontic instrument having regressive conicity

Abstract

A method and apparatus for extirpating tissue from a radicular dental canal comprises a set of instruments having graduated lengths and diameters. In one embodiment of the invention, one instrument is of such length to extirpate the apical foramen. This full depth instrument has a first cutting length that conforms to a first taper angle between a conical apex and a first base diameter. The first cutting length is less than the length of the root canal. Above the first cutting length, the instrument may be cylindrical. The full depth instrument is followed by a second instrument having a length that is less than that of the full length instrument by the length of the first cutting length. The second instrument cutting length is also less than the length of the root canal and extends between a minor diameter at the tip of the instrument and minor diameter at the longitudinal end of the cutting length. The second instrument minor diameter is substantially the same as the major diameter of the full depth instrument.

I claim:  
     
       1. A sequential plurality of endodontic instruments comprising a set for extirpating radicular dental canals, each instrument in said set having a working length that includes a shank portion and a tapered end portion, said tapered end portion having a diminishing diameter along a cutting length between a first diameter and second diameter, said first diameter being proximate of a region of integral juncture of said tapered end portion with said shank portion and said second diameter being proximate of a tapered end portion terminus, the second diameter for a first instrument in the sequential plurality of said set substantially being an apex terminus and subsequent instruments in the sequence having a second diameter substantially corresponding to the first diameter of a sequentially adjacent instrument, wherein the working length of each subsequent instrument in said set is less than the working length of a sequentially adjacent instrument by a distance that substantially corresponds to the cutting length of the tapered end portion of said sequentially adjacent instrument. 
     
     
       2. A set of endodontic instruments as described in claim  1  wherein the tapered end portion of each instrument in said set substantially conforms to a respective conical angle. 
     
     
       3. A set of endodontic instruments as described by claim  2  wherein the tapered end portion of all instruments in said set substantially conform to the same conical angle. 
     
     
       4. A set of endodontic instruments as described by claim  2  wherein the tapered end portion of each instrument in said set substantially conforms to a different conical angle. 
     
     
       5. A set of endodontic instruments as described by claim  1  wherein a first conical angle respective to the tapered end portion of an instrument is substantially the same for all instruments in said set. 
     
     
       6. A set of endodontic instruments as described by claim  5  wherein outer surface elements about a perimeter of said shank portion are substantially parallel. 
     
     
       7. A set of endodontic instruments as described by claim  5  wherein outer surface elements about a perimeter of said shank portion substantially circumscribe the frustum of a cone having a second conical angle that is less than said first conical angle. 
     
     
       8. A set of endodontic instruments as described by claim  1  wherein a terminal end portion respective to subsequent instruments in the sequence comprises non-cutting surfaces. 
     
     
       9. A set of endodontic instruments as described by claim  1  wherein the second diameter for subsequent instruments in said sequence circumscribes a non-cutting tip. 
     
     
       10. A method of extirpating radicular dental canals comprising the steps of: 
       extirpating tissue from a root canal length along a first boring that substantially terminates proximate of a distal tip of the canal with a first instrument having a tapered end portion with a cutting length forming a substantially conical first extirpation volume, said first extirpation volume expanding from a substantial apex with a first conical angle along a first conical length less than said root canal length to a first conical base having a first canal diameter; and,  
       extirpating tissue from said root canal along said canal length in at least one different conical length increment with a second instrument having a second working length, said different conical length increment being less than said canal length and delineating a conical frustum having said first conical angle and said second working length being less than said first working length by a distance that substantially corresponds to the cutting length of the tapered end portion of said first instrument.  
     
     
       11. A method as described by claim  10  wherein the conical frustum respective to each of said different length increments has a major diameter at one end of said length increment and a minor diameter less than said major diameter at an opposite end of the length increment, the minor diameter of an increment substantially corresponding to the major diameter of a serially preceding increment. 
     
     
       12. A method as described by claim  11  wherein tissue extirpation along said canal length is substantially limited to the length of each conical frustrum, sequentially. 
     
     
       13. An endodontic instrument for extirpating radicular dental canals, said instrument including a shaft comprising: 
       a proximal end, a distal end, and a fluted working portion located between said proximal and distal ends, said fluted working portion including a tapered cutting surface located adjacent said distal end and increasing in diameter in a proximal direction from a minor diameter to a larger, major diameter, and a fluted proximal portion located between said tapered cutting surface and said proximal end, said fluted proximal portion having a zero taper angle configured to carry debris away from said distal end without substantially cutting tissue during a cutting movement of said shaft.  
     
     
       14. The endodontic instrument of claim  13 , wherein said distal end forms a conical frustum. 
     
     
       15. The endodontic instrument of claim  13 , wherein said distal end is a tip forming a substantial apex. 
     
     
       16. A set of endodontic instruments for extirpating radicular dental canals, each instrument in said set having a shaft with a proximal end, a distal end and a working length therebetween that includes a tapered cutting surface adjacent said distal end, said tapered cutting surface having a cutting length extending from a first diameter to a second, smaller diameter located at said distal end, the second diameter for a first instrument in said set substantially being an apex terminus and subsequent instruments in said set having a second diameter substantially corresponding to the first diameter of a sequentially adjacent instrument, at least one of said instruments including a fluted proximal portion located proximally of said tapered cutting surface and having a zero taper angle such that said fluted proximal portion carries debris away from said distal end without substantially cutting tissue during a cutting movement of said shaft. 
     
     
       17. A method of extirpating a radicular dental canal with an instrument including a shaft having a proximal end and a distal end defined along an axis of movement, and a fluted working portion located between the proximal and distal ends, the fluted working portion including a tapered cutting surface located adjacent the distal end and increasing in diameter in a proximal direction from a minor diameter to a larger, major diameter, and a fluted proximal portion located between the tapered cutting surface and the proximal end, the fluted proximal portion having a zero taper angle, the method comprising the steps of: 
       inserting the fluted working portion of the instrument into the radicular dental canal,  
       cutting tissue within the radicular dental canal with the tapered cutting surface, and  
       directing tissue debris away from the distal end along the fluted proximal portion.